io_uring/waitid.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Support for async notification of waitid
  */
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/fs.h>
 #include <linux/file.h>
 #include <linux/compat.h>
 #include <linux/io_uring.h>

 #include <uapi/linux/io_uring.h>

 #include "io_uring.h"
 #include "cancel.h"
 #include "waitid.h"
 #include "../kernel/exit.h"

 static void io_waitid_cb(struct io_kiocb *req, struct io_tw_state *ts);

 #define IO_WAITID_CANCEL_FLAG	BIT(31)
 #define IO_WAITID_REF_MASK	GENMASK(30, 0)

 struct io_waitid {
 	struct file *file;
 	int which;
 	pid_t upid;
 	int options;
 	atomic_t refs;
 	struct wait_queue_head *head;
 	struct siginfo __user *infop;
 	struct waitid_info info;
 };

 static void io_waitid_free(struct io_kiocb *req)
 {
 	struct io_waitid_async *iwa = req->async_data;

 	put_pid(iwa->wo.wo_pid);
 	kfree(req->async_data);
 	req->async_data = NULL;
 	req->flags &= ~REQ_F_ASYNC_DATA;
 }

 #ifdef CONFIG_COMPAT
 static bool io_waitid_compat_copy_si(struct io_waitid *iw, int signo)
 {
 	struct compat_siginfo __user *infop;
 	bool ret;

 	infop = (struct compat_siginfo __user *) iw->infop;

 	if (!user_write_access_begin(infop, sizeof(*infop)))
 		return false;

 	unsafe_put_user(signo, &infop->si_signo, Efault);
 	unsafe_put_user(0, &infop->si_errno, Efault);
 	unsafe_put_user(iw->info.cause, &infop->si_code, Efault);
 	unsafe_put_user(iw->info.pid, &infop->si_pid, Efault);
 	unsafe_put_user(iw->info.uid, &infop->si_uid, Efault);
 	unsafe_put_user(iw->info.status, &infop->si_status, Efault);
 	ret = true;
 done:
 	user_write_access_end();
 	return ret;
 Efault:
 	ret = false;
 	goto done;
 }
 #endif

 static bool io_waitid_copy_si(struct io_kiocb *req, int signo)
 {
 	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
 	bool ret;

 	if (!iw->infop)
 		return true;

 #ifdef CONFIG_COMPAT
 	if (req->ctx->compat)
 		return io_waitid_compat_copy_si(iw, signo);
 #endif

 	if (!user_write_access_begin(iw->infop, sizeof(*iw->infop)))
 		return false;

 	unsafe_put_user(signo, &iw->infop->si_signo, Efault);
 	unsafe_put_user(0, &iw->infop->si_errno, Efault);
 	unsafe_put_user(iw->info.cause, &iw->infop->si_code, Efault);
 	unsafe_put_user(iw->info.pid, &iw->infop->si_pid, Efault);
 	unsafe_put_user(iw->info.uid, &iw->infop->si_uid, Efault);
 	unsafe_put_user(iw->info.status, &iw->infop->si_status, Efault);
 	ret = true;
 done:
 	user_write_access_end();
 	return ret;
 Efault:
 	ret = false;
 	goto done;
 }

 static int io_waitid_finish(struct io_kiocb *req, int ret)
 {
 	int signo = 0;

 	if (ret > 0) {
 		signo = SIGCHLD;
 		ret = 0;
 	}

 	if (!io_waitid_copy_si(req, signo))
 		ret = -EFAULT;
 	io_waitid_free(req);
 	return ret;
 }

 static void io_waitid_complete(struct io_kiocb *req, int ret)
 {
 	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
 	struct io_tw_state ts = { .locked = true };

 	/* anyone completing better be holding a reference */
 	WARN_ON_ONCE(!(atomic_read(&iw->refs) & IO_WAITID_REF_MASK));

 	lockdep_assert_held(&req->ctx->uring_lock);

 	hlist_del_init(&req->hash_node);

 	ret = io_waitid_finish(req, ret);
 	if (ret < 0)
 		req_set_fail(req);
 	io_req_set_res(req, ret, 0);
 	io_req_task_complete(req, &ts);
 }

 static bool __io_waitid_cancel(struct io_ring_ctx *ctx, struct io_kiocb *req)
 {
 	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
 	struct io_waitid_async *iwa = req->async_data;

 	/*
 	 * Mark us canceled regardless of ownership. This will prevent a
 	 * potential retry from a spurious wakeup.
 	 */
 	atomic_or(IO_WAITID_CANCEL_FLAG, &iw->refs);

 	/* claim ownership */
 	if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK)
 		return false;

 	spin_lock_irq(&iw->head->lock);
 	list_del_init(&iwa->wo.child_wait.entry);
 	spin_unlock_irq(&iw->head->lock);
 	io_waitid_complete(req, -ECANCELED);
 	return true;
 }

 int io_waitid_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd,
 		     unsigned int issue_flags)
 {
 	struct hlist_node *tmp;
 	struct io_kiocb *req;
 	int nr = 0;

 	if (cd->flags & (IORING_ASYNC_CANCEL_FD|IORING_ASYNC_CANCEL_FD_FIXED))
 		return -ENOENT;

 	io_ring_submit_lock(ctx, issue_flags);
 	hlist_for_each_entry_safe(req, tmp, &ctx->waitid_list, hash_node) {
 		if (req->cqe.user_data != cd->data &&
 		    !(cd->flags & IORING_ASYNC_CANCEL_ANY))
 			continue;
 		if (__io_waitid_cancel(ctx, req))
 			nr++;
 		if (!(cd->flags & IORING_ASYNC_CANCEL_ALL))
 			break;
 	}
 	io_ring_submit_unlock(ctx, issue_flags);

 	if (nr)
 		return nr;

 	return -ENOENT;
 }

 bool io_waitid_remove_all(struct io_ring_ctx *ctx, struct task_struct *task,
 			  bool cancel_all)
 {
 	struct hlist_node *tmp;
 	struct io_kiocb *req;
 	bool found = false;

 	lockdep_assert_held(&ctx->uring_lock);

 	hlist_for_each_entry_safe(req, tmp, &ctx->waitid_list, hash_node) {
 		if (!io_match_task_safe(req, task, cancel_all))
 			continue;
 		hlist_del_init(&req->hash_node);
 		__io_waitid_cancel(ctx, req);
 		found = true;
 	}

 	return found;
 }

 static inline bool io_waitid_drop_issue_ref(struct io_kiocb *req)
 {
 	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
 	struct io_waitid_async *iwa = req->async_data;

 	if (!atomic_sub_return(1, &iw->refs))
 		return false;

 	/*
 	 * Wakeup triggered, racing with us. It was prevented from
 	 * completing because of that, queue up the tw to do that.
 	 */
 	req->io_task_work.func = io_waitid_cb;
 	io_req_task_work_add(req);
 	remove_wait_queue(iw->head, &iwa->wo.child_wait);
 	return true;
 }

 static void io_waitid_cb(struct io_kiocb *req, struct io_tw_state *ts)
 {
 	struct io_waitid_async *iwa = req->async_data;
 	struct io_ring_ctx *ctx = req->ctx;
 	int ret;

 	io_tw_lock(ctx, ts);

 	ret = __do_wait(&iwa->wo);

 	/*
 	 * If we get -ERESTARTSYS here, we need to re-arm and check again
 	 * to ensure we get another callback. If the retry works, then we can
 	 * just remove ourselves from the waitqueue again and finish the
 	 * request.
 	 */
 	if (unlikely(ret == -ERESTARTSYS)) {
 		struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);

 		/* Don't retry if cancel found it meanwhile */
 		ret = -ECANCELED;
 		if (!(atomic_read(&iw->refs) & IO_WAITID_CANCEL_FLAG)) {
 			iw->head = &current->signal->wait_chldexit;
 			add_wait_queue(iw->head, &iwa->wo.child_wait);
 			ret = __do_wait(&iwa->wo);
 			if (ret == -ERESTARTSYS) {
 				/* retry armed, drop our ref */
 				io_waitid_drop_issue_ref(req);
 				return;
 			}

 			remove_wait_queue(iw->head, &iwa->wo.child_wait);
 		}
 	}

 	io_waitid_complete(req, ret);
 }

 static int io_waitid_wait(struct wait_queue_entry *wait, unsigned mode,
 			  int sync, void *key)
 {
 	struct wait_opts *wo = container_of(wait, struct wait_opts, child_wait);
 	struct io_waitid_async *iwa = container_of(wo, struct io_waitid_async, wo);
 	struct io_kiocb *req = iwa->req;
 	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
 	struct task_struct *p = key;

 	if (!pid_child_should_wake(wo, p))
 		return 0;

 	/* cancel is in progress */
 	if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK)
 		return 1;

 	req->io_task_work.func = io_waitid_cb;
 	io_req_task_work_add(req);
 	list_del_init(&wait->entry);
 	return 1;
 }

 int io_waitid_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);

 	if (sqe->addr || sqe->buf_index || sqe->addr3 || sqe->waitid_flags)
 		return -EINVAL;

 	iw->which = READ_ONCE(sqe->len);
 	iw->upid = READ_ONCE(sqe->fd);
 	iw->options = READ_ONCE(sqe->file_index);
 	iw->infop = u64_to_user_ptr(READ_ONCE(sqe->addr2));
 	return 0;
 }

 int io_waitid(struct io_kiocb *req, unsigned int issue_flags)
 {
 	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
 	struct io_ring_ctx *ctx = req->ctx;
 	struct io_waitid_async *iwa;
 	int ret;

 	if (io_alloc_async_data(req))
 		return -ENOMEM;

 	iwa = req->async_data;
 	iwa->req = req;

 	ret = kernel_waitid_prepare(&iwa->wo, iw->which, iw->upid, &iw->info,
 					iw->options, NULL);
 	if (ret)
 		goto done;

 	/*
 	 * Mark the request as busy upfront, in case we're racing with the
 	 * wakeup. If we are, then we'll notice when we drop this initial
 	 * reference again after arming.
 	 */
 	atomic_set(&iw->refs, 1);

 	/*
 	 * Cancel must hold the ctx lock, so there's no risk of cancelation
 	 * finding us until a) we remain on the list, and b) the lock is
 	 * dropped. We only need to worry about racing with the wakeup
 	 * callback.
 	 */
 	io_ring_submit_lock(ctx, issue_flags);
 	hlist_add_head(&req->hash_node, &ctx->waitid_list);

 	init_waitqueue_func_entry(&iwa->wo.child_wait, io_waitid_wait);
 	iwa->wo.child_wait.private = req->task;
 	iw->head = &current->signal->wait_chldexit;
 	add_wait_queue(iw->head, &iwa->wo.child_wait);

 	ret = __do_wait(&iwa->wo);
 	if (ret == -ERESTARTSYS) {
 		/*
 		 * Nobody else grabbed a reference, it'll complete when we get
 		 * a waitqueue callback, or if someone cancels it.
 		 */
 		if (!io_waitid_drop_issue_ref(req)) {
 			io_ring_submit_unlock(ctx, issue_flags);
 			return IOU_ISSUE_SKIP_COMPLETE;
 		}

 		/*
 		 * Wakeup triggered, racing with us. It was prevented from
 		 * completing because of that, queue up the tw to do that.
 		 */
 		io_ring_submit_unlock(ctx, issue_flags);
 		return IOU_ISSUE_SKIP_COMPLETE;
 	}

 	hlist_del_init(&req->hash_node);
 	remove_wait_queue(iw->head, &iwa->wo.child_wait);
 	ret = io_waitid_finish(req, ret);

 	io_ring_submit_unlock(ctx, issue_flags);
 done:
 	if (ret < 0)
 		req_set_fail(req);
 	io_req_set_res(req, ret, 0);
 	return IOU_OK;
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Support for async notification of waitid
	*/
	#include <linux/kernel.h>
	#include <linux/errno.h>
	#include <linux/fs.h>
	#include <linux/file.h>
	#include <linux/compat.h>
	#include <linux/io_uring.h>

	#include <uapi/linux/io_uring.h>

	#include "io_uring.h"
	#include "cancel.h"
	#include "waitid.h"
	#include "../kernel/exit.h"

	static void io_waitid_cb(struct io_kiocb req, struct io_tw_state ts);

	#define IO_WAITID_CANCEL_FLAG BIT(31)
	#define IO_WAITID_REF_MASK GENMASK(30, 0)

	struct io_waitid {
	struct file *file;
	int which;
	pid_t upid;
	int options;
	atomic_t refs;
	struct wait_queue_head *head;
	struct siginfo __user *infop;
	struct waitid_info info;
	};

	static void io_waitid_free(struct io_kiocb *req)
	{
	struct io_waitid_async *iwa = req->async_data;

	put_pid(iwa->wo.wo_pid);
	kfree(req->async_data);
	req->async_data = NULL;
	req->flags &= ~REQ_F_ASYNC_DATA;
	}

	#ifdef CONFIG_COMPAT
	static bool io_waitid_compat_copy_si(struct io_waitid *iw, int signo)
	{
	struct compat_siginfo __user *infop;
	bool ret;

	infop = (struct compat_siginfo __user *) iw->infop;

	if (!user_write_access_begin(infop, sizeof(*infop)))
	return false;

	unsafe_put_user(signo, &infop->si_signo, Efault);
	unsafe_put_user(0, &infop->si_errno, Efault);
	unsafe_put_user(iw->info.cause, &infop->si_code, Efault);
	unsafe_put_user(iw->info.pid, &infop->si_pid, Efault);
	unsafe_put_user(iw->info.uid, &infop->si_uid, Efault);
	unsafe_put_user(iw->info.status, &infop->si_status, Efault);
	ret = true;
	done:
	user_write_access_end();
	return ret;
	Efault:
	ret = false;
	goto done;
	}
	#endif

	static bool io_waitid_copy_si(struct io_kiocb *req, int signo)
	{
	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
	bool ret;

	if (!iw->infop)
	return true;

	#ifdef CONFIG_COMPAT
	if (req->ctx->compat)
	return io_waitid_compat_copy_si(iw, signo);
	#endif

	if (!user_write_access_begin(iw->infop, sizeof(*iw->infop)))
	return false;

	unsafe_put_user(signo, &iw->infop->si_signo, Efault);
	unsafe_put_user(0, &iw->infop->si_errno, Efault);
	unsafe_put_user(iw->info.cause, &iw->infop->si_code, Efault);
	unsafe_put_user(iw->info.pid, &iw->infop->si_pid, Efault);
	unsafe_put_user(iw->info.uid, &iw->infop->si_uid, Efault);
	unsafe_put_user(iw->info.status, &iw->infop->si_status, Efault);
	ret = true;
	done:
	user_write_access_end();
	return ret;
	Efault:
	ret = false;
	goto done;
	}

	static int io_waitid_finish(struct io_kiocb *req, int ret)
	{
	int signo = 0;

	if (ret > 0) {
	signo = SIGCHLD;
	ret = 0;
	}

	if (!io_waitid_copy_si(req, signo))
	ret = -EFAULT;
	io_waitid_free(req);
	return ret;
	}

	static void io_waitid_complete(struct io_kiocb *req, int ret)
	{
	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
	struct io_tw_state ts = { .locked = true };

	/* anyone completing better be holding a reference */
	WARN_ON_ONCE(!(atomic_read(&iw->refs) & IO_WAITID_REF_MASK));

	lockdep_assert_held(&req->ctx->uring_lock);

	hlist_del_init(&req->hash_node);

	ret = io_waitid_finish(req, ret);
	if (ret < 0)
	req_set_fail(req);
	io_req_set_res(req, ret, 0);
	io_req_task_complete(req, &ts);
	}

	static bool __io_waitid_cancel(struct io_ring_ctx ctx, struct io_kiocb req)
	{
	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
	struct io_waitid_async *iwa = req->async_data;

	/*
	* Mark us canceled regardless of ownership. This will prevent a
	* potential retry from a spurious wakeup.
	*/
	atomic_or(IO_WAITID_CANCEL_FLAG, &iw->refs);

	/* claim ownership */
	if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK)
	return false;

	spin_lock_irq(&iw->head->lock);
	list_del_init(&iwa->wo.child_wait.entry);
	spin_unlock_irq(&iw->head->lock);
	io_waitid_complete(req, -ECANCELED);
	return true;
	}

	int io_waitid_cancel(struct io_ring_ctx ctx, struct io_cancel_data cd,
	unsigned int issue_flags)
	{
	struct hlist_node *tmp;
	struct io_kiocb *req;
	int nr = 0;

	if (cd->flags & (IORING_ASYNC_CANCEL_FD\|IORING_ASYNC_CANCEL_FD_FIXED))
	return -ENOENT;

	io_ring_submit_lock(ctx, issue_flags);
	hlist_for_each_entry_safe(req, tmp, &ctx->waitid_list, hash_node) {
	if (req->cqe.user_data != cd->data &&
	!(cd->flags & IORING_ASYNC_CANCEL_ANY))
	continue;
	if (__io_waitid_cancel(ctx, req))
	nr++;
	if (!(cd->flags & IORING_ASYNC_CANCEL_ALL))
	break;
	}
	io_ring_submit_unlock(ctx, issue_flags);

	if (nr)
	return nr;

	return -ENOENT;
	}

	bool io_waitid_remove_all(struct io_ring_ctx ctx, struct task_struct task,
	bool cancel_all)
	{
	struct hlist_node *tmp;
	struct io_kiocb *req;
	bool found = false;

	lockdep_assert_held(&ctx->uring_lock);

	hlist_for_each_entry_safe(req, tmp, &ctx->waitid_list, hash_node) {
	if (!io_match_task_safe(req, task, cancel_all))
	continue;
	hlist_del_init(&req->hash_node);
	__io_waitid_cancel(ctx, req);
	found = true;
	}

	return found;
	}

	static inline bool io_waitid_drop_issue_ref(struct io_kiocb *req)
	{
	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
	struct io_waitid_async *iwa = req->async_data;

	if (!atomic_sub_return(1, &iw->refs))
	return false;

	/*
	* Wakeup triggered, racing with us. It was prevented from
	* completing because of that, queue up the tw to do that.
	*/
	req->io_task_work.func = io_waitid_cb;
	io_req_task_work_add(req);
	remove_wait_queue(iw->head, &iwa->wo.child_wait);
	return true;
	}

	static void io_waitid_cb(struct io_kiocb req, struct io_tw_state ts)
	{
	struct io_waitid_async *iwa = req->async_data;
	struct io_ring_ctx *ctx = req->ctx;
	int ret;

	io_tw_lock(ctx, ts);

	ret = __do_wait(&iwa->wo);

	/*
	* If we get -ERESTARTSYS here, we need to re-arm and check again
	* to ensure we get another callback. If the retry works, then we can
	* just remove ourselves from the waitqueue again and finish the
	* request.
	*/
	if (unlikely(ret == -ERESTARTSYS)) {
	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);

	/* Don't retry if cancel found it meanwhile */
	ret = -ECANCELED;
	if (!(atomic_read(&iw->refs) & IO_WAITID_CANCEL_FLAG)) {
	iw->head = &current->signal->wait_chldexit;
	add_wait_queue(iw->head, &iwa->wo.child_wait);
	ret = __do_wait(&iwa->wo);
	if (ret == -ERESTARTSYS) {
	/* retry armed, drop our ref */
	io_waitid_drop_issue_ref(req);
	return;
	}

	remove_wait_queue(iw->head, &iwa->wo.child_wait);
	}
	}

	io_waitid_complete(req, ret);
	}

	static int io_waitid_wait(struct wait_queue_entry *wait, unsigned mode,
	int sync, void *key)
	{
	struct wait_opts *wo = container_of(wait, struct wait_opts, child_wait);
	struct io_waitid_async *iwa = container_of(wo, struct io_waitid_async, wo);
	struct io_kiocb *req = iwa->req;
	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
	struct task_struct *p = key;

	if (!pid_child_should_wake(wo, p))
	return 0;

	/* cancel is in progress */
	if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK)
	return 1;

	req->io_task_work.func = io_waitid_cb;
	io_req_task_work_add(req);
	list_del_init(&wait->entry);
	return 1;
	}

	int io_waitid_prep(struct io_kiocb req, const struct io_uring_sqe sqe)
	{
	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);

	if (sqe->addr \|\| sqe->buf_index \|\| sqe->addr3 \|\| sqe->waitid_flags)
	return -EINVAL;

	iw->which = READ_ONCE(sqe->len);
	iw->upid = READ_ONCE(sqe->fd);
	iw->options = READ_ONCE(sqe->file_index);
	iw->infop = u64_to_user_ptr(READ_ONCE(sqe->addr2));
	return 0;
	}

	int io_waitid(struct io_kiocb *req, unsigned int issue_flags)
	{
	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
	struct io_ring_ctx *ctx = req->ctx;
	struct io_waitid_async *iwa;
	int ret;

	if (io_alloc_async_data(req))
	return -ENOMEM;

	iwa = req->async_data;
	iwa->req = req;

	ret = kernel_waitid_prepare(&iwa->wo, iw->which, iw->upid, &iw->info,
	iw->options, NULL);
	if (ret)
	goto done;

	/*
	* Mark the request as busy upfront, in case we're racing with the
	* wakeup. If we are, then we'll notice when we drop this initial
	* reference again after arming.
	*/
	atomic_set(&iw->refs, 1);

	/*
	* Cancel must hold the ctx lock, so there's no risk of cancelation
	* finding us until a) we remain on the list, and b) the lock is
	* dropped. We only need to worry about racing with the wakeup
	* callback.
	*/
	io_ring_submit_lock(ctx, issue_flags);
	hlist_add_head(&req->hash_node, &ctx->waitid_list);

	init_waitqueue_func_entry(&iwa->wo.child_wait, io_waitid_wait);
	iwa->wo.child_wait.private = req->task;
	iw->head = &current->signal->wait_chldexit;
	add_wait_queue(iw->head, &iwa->wo.child_wait);

	ret = __do_wait(&iwa->wo);
	if (ret == -ERESTARTSYS) {
	/*
	* Nobody else grabbed a reference, it'll complete when we get
	* a waitqueue callback, or if someone cancels it.
	*/
	if (!io_waitid_drop_issue_ref(req)) {
	io_ring_submit_unlock(ctx, issue_flags);
	return IOU_ISSUE_SKIP_COMPLETE;
	}

	/*
	* Wakeup triggered, racing with us. It was prevented from
	* completing because of that, queue up the tw to do that.
	*/
	io_ring_submit_unlock(ctx, issue_flags);
	return IOU_ISSUE_SKIP_COMPLETE;
	}

	hlist_del_init(&req->hash_node);
	remove_wait_queue(iw->head, &iwa->wo.child_wait);
	ret = io_waitid_finish(req, ret);

	io_ring_submit_unlock(ctx, issue_flags);
	done:
	if (ret < 0)
	req_set_fail(req);
	io_req_set_res(req, ret, 0);
	return IOU_OK;
	}